Hi and welcome.
Just being one of the ones committed to staying on this site...and not disappearing quickly....will be a fantastic start for you. I think the ones who leave feel defeated within days......and just staying here alone will start you off on the right foot.
And there are so many reasons. There is just a ton of info here....literally info on every diet/eating plan under the sun...also exercise info, etc. There's something for everyone. Then there's the being accountable...that's a biggie. And then there's the support and motivation. Checking out the success stories, especially the before and after pics is a huge motivator....and gives you an "if they did it, so can I" attitude.
Now...even though I've been/am active on several other message boards for several years, I felt a bit intimidated when I first arrived here. But now I think that what intimidated me turned out to be one of the huge positives here. The other message boards I am/have been on....whether they had a huge active membership or not....all of the forums on the main page applied to everyone and everyone was active on all of them...it was the nature of the topic....so there developed cliques, in-crowd and out crowd, etc.
But here, even though it seems like a huge city at first, the big advantage is that there seem to be individual communities on the different forums...esp. the ones for the various diets/eating plans and also the individual support forums for different needs/age/stats. And this ends up not only preventing the in-crowd/out-crowd situation....but every member here can find their own little community where they make their own friends and get into a posting/support relationship with.
deena